Voice operated gain adjuster



May 2, 1933. E. M. STAPLES VOICE OPERATED GAIN ADJUSTERl Filed Dec. 23,1931 FTS INVENToR EMS/@laks Bv ATTORNEY Patented` -May 2,- 1933 fVUNITEDST.1\fr1:s

PATENT. ,j

ELLIOT M. s'rArnEs, oF HoHoxUs NEW JERSEY, `AssIciNoR TOY-AMERICANTELEI- PHONEAND TELEGRAPH COMPANY-,:AcoRPoRATIoNaoE NEW vom:Y .j y

voIcE OPERATED GAINpADJUsTER Ap-Plriaatmn mea December y2s, 1931.semina.. 582,896.;

. Among the objects ofmy inventionis to .provide a Vnew and improvedmethod and` corresponding apparatus for adjusting the gain of anamplifier in a signal transmitting `5 system. Anotherfobject ofiny'invention is to provide foradjusting theegain in accordance with thefrequency of occurrence'.- of voltage peaks. Still. another object is tocount voltagefpeaks on the output side of an amplifierl and adjust theinput thereto so as keep the number of suchpeaks as nearly aspracticable in yconstant ratio -to elapsed time. All these objects andvarious other objects and advantages of my, invention will become`apparent on consideration of the following disclosure V.of a specificexample of practice in accordance with .the invention. `It will beunderstood that the following .disclosure relates principally to thisparticular examf ple ofmy invention and-that itsscope will be indicatedinthe appended claims.

Referring to the drawing, this is a diagram of an amplifier andassociated apparatus with which my invention may*v be practiced.

The amplifier k14 lies between the pair of input terminals 11, 12 andthepair of output terminals 15, 16. Apotentiometer `13 isy introduced onthe input side and it will readily be seen that by adjustment ofthe armof the switch B, stepsof'resistance-are transferred from series to shuntand vice versa. f

The detector 18' is connected .across the 35 line through the switches19`on the output side of the amplier 14. This detector 18-isj .adjustedso Athat any currents on the line above a certain low level will causeenoughr current to How through the relayC to close input side, that isin its grid circuit, is

adjusted so that at a certaindesired voltage the `tube will flash over,that is give a sudden'current rush in the plate circuit containingtherelay 22, This relayis slow acting.` It and likewise the other relayspresently -to require V0.2'second to operate and 0.3 ,secondA torelease.V When the flash-over currentA in the ouput circuit of the gastube 21 operates j the relay 22,.it opens its own circuit at23 'co Ithe' right.` The release relay 29 steps this arm one step to the left,but release relay 25-25 returns' the-arm 24 all the wayV to n thev leftkeven if relay 22 is operated. The switch arm 26y is driven by a motor orclock so as to makeone revolution in 5 seconds. At one pointin eachrevolution it makes contact withthe grounded metallic segment 27( for aperiod long enough to operatek relays 28or29. f y p Further details ofstructure will'become apparent., in connection with the followingdescription ofthe operation'of the system. 'JUase' 1..-As willbe seenwhen all casesV havezbeenl considered-arm 24 lwillY be left on the 0lpoint immediately after arm 26 engages segment 27. Suppose that-during asingle rotation of the arm 26 from 27 around again yto 27 there'is oneand only one'voltage peak in the plate circuit of the gasvtube 21 ofsuiiicient intensity to operate relay 22. This single operation of therelay 22 willstepthe arm24: of switch A from `its `0 point to point1,-where itwill remain .untilV the arm. 26 again reaches the segment 27Thereupon a'circuit will be closed from ground throughv segment n 27,arm 26, front contact of 'relay `C,winding 25 of relay 25-25, point 1oflswitch A, arm 24v and battery to ground.y The corresponding im'-pulse of currentin the circuit just traced, energizing the relay .25-25,will. return the switch arm24 toits O point.l .In this lcase no,adjustment of the potentiometer switch B will be made, andv aslong asthere.:

is a recurrence of one and only one effective voltage peak per 5 secondinterval, no adjustment will be made at B. Each time the switch arm 24will step from its 0 point 5 to point l and then at the end of the 5second interval drop back to its point. One such voltage peak per secondinterval is considered to indicate a proper gain adjustn ment of theamplier 14.

Oase {If-Suppose that during such a 5 second period of rotation of theswitch arm 26 from the segment 27 around and back to the segment 27there is no voltage peak sufhcient to operate the relay 22 in the outputcircuit of the gas tube 2l. Then `the arm 24 will remain on the 0 pointof the switch A, and when the arm 26 arrives at the segment 27 at theend of the 5 second period a circuit will be closed as follows:

From ground through segment 27, arm 26, front contact of relay C,release relay 29,

Y 0 point of switch A, its arm 24, and through battery to ground; Thecorresponding current impulse in the relay 29 will step the arm ofswitch B one step to the left, thus transferring a step of resistance 13from series to shunt and increasing the intensity of the amplifierinput, that is increasingthe over-all gain. Each time that a 5 second 30interval passes without an effective voltage peak, the arm of the switchB will be stepped one point to the left until it reaches the end of itspossible travel in that direction, putting all the resistance in shuntand none in 3.5 in series. The absence of a voltage peak in a 5 secondinterval is deemed to indicate that the amplifier 14 is not givingenough gaip and the adjustment is made accord- 1n t(ase I I I .-Supposethat during a 5 second interval, as determined by the rotation of theswitch arm 26 from segment 27 around again to segment 27, there are twoor more effective voltage peaks; thus, the arm 24 of switch A will hestepped twice to the right and will rest on point 2 when the arm 26arrives at the segment 27. Thereupon a circuit will be closed fromground through segment 27, arm 26, front contact of relay 5U C, relay28, point 2 of switch A, its arm 24,

and through battery to ground. The corresponding current impulse in therelay 28 will step the arm of switch B one step to the right, thustransferring a step of resistance from shunt to series and therebydecreasing the over-all gain of the amplifier 14. It is considered thatif effective voltage `peaks occur as often as twice in a 5 secondinterval, this means that the amplifier gain is too high and requires anadjustment downward. The energization of the relay 28 also closes aContact at 30, thus putting battery to a circuit through the winding 25of relay 25-25 Vwhich restores the arm 24 of switch 65 A to its 0 point.

Briefly summarized, the operation involves increasing the gain, orleaving it unchanged, or decreasing it according as the number ofeffective voltage peaks is none per 5 second period, or one, or morethan one. If there is over-adjustment one way due to fortuitous scarcityor frequency of voltage peaks in a 5 second period, it will be quicklycorrected the other way in ensuing 5 second intervals. On an average,that is in the long run, 'the potentiometer 'i3 will be heldr at suchadjustment that voltage peaks will occur at the rate of once per 5second interval.

The detector 18 as connected in the system prevents adjustment whenthere are no voice currents on the line. lt can be omitted by openingthe switches 19 and shifting the switch 20. lVhen it is omitted in thisway and there is no speech on the line, then there will be an absence ofvoltage peaks and in each 5 second period there will be an adjustmentdescribed above for Case II, so that eventually the amplifier 14 will beadjusted for the utmost gain. .Then when speech starts, the necessarysteps of adjustmentdown will quickly be made to bring the arnplilieroutput to the proper level.

That is claimed is:

l, The method of adjusting for gain which consists in counting voltagepeaks above a certain degree of intensity, holding the gain unchangedwhen these peaks occur at a certain time rate, increasing' the gain whenthey occur less frequently, and decreasing the gain when they occur morefrequently.

2. The method of adjusting for gain which consists in holding the gainunchanged when a voltage peak of as much as a certain degree ofintensity occurs once in each of certain successive equal intervals oftime, increasing the gain a step when no such peak occurs in such aperiod, and de creasing the gain a step when more than one such peakoccurs in such a period.

3. The method of holding a certain desired power level at a certainpoint of a transmission line which consists in making gain adjustmentsin steps, with an added step when no voltage peak above a certainintensity occurs at that point within a certain period of time, with nostep either way when there is one such voltage peak in said period, andwith a subtracted step when there are more than one such peak in saidperiod.

4. The method of adjusting for gain which consists in keeping theadjustment unchanged when voltage peaks above a certain degree ofintensity occur at a certain rate and adjusting to increase or decreasethe gain when these peaks are respectively less frequent or morefrequent.

5. An amplifier adjustable for gain, a device responsive to voltagepeaks above a certain degree of intensity .in the amplifier output, anda connectiontherefrom to adjust the amplifier, said connectioncomprising time lapse means to 'make adjustment dependent on frequencyof response of the said device. f

6. An amplifier, means to adjust itsgain in steps, a device responsivetovoltage peaks above-a certain degree of intensity on rits output side, arelay controlled accordingly by said device, a motor driven commutator,kand means controlled jointly by said relay and commutator to adjust saidfirst mentioned means for gain according to the relan tive frequency ofoccurrence of the voltage peaks.

7. An amplifier, means to adjust it for gain, a deviceconnected on itsoutput side and responsive to voltage peaks above a certain intensity, acounting mechanism I to count such voltage.. peaks to 0, 1 kor 2, amotor driven commutator, and circuit vconnections to actuate said meansfor adjusting the amplifier according to the count in the countingmechanism and the completion of i,

a time cycle in the commutator.

In testimony whereof, I have signed myy name to this specification this22nd day of December 1931.

ELLIOT'M. STAPLES.

